What dimensions should my image be to get printed on a 2.25" button?

I'm trying to figure out what the dimensions should be, but I cant. Both of the images i want to submit are over 500 x 500 px, but less than 640 x 640 px. The seller says that its best if the image is 300 dpi, but clearly I don't understand that and they did not put any information on that.

What is a drawing game that comes with a pair of drunk goggles and you have to pick a card and draw the word on the card while wearing them?

Surface 2 good tablet for me?

Hey guys!
I am a sort of amateurish artist and am on a budget. People always talk about how amazing the surface pro 2 and 3 are for digital drawing but they are pretty expensive. Do you think the surface 2 would be alright for drawing digitally?

does nikkor af 50mm f/1.8g and the nikkor af 35mm f/1.8g both have marking on their focus rings?